A programmed-defect mask consisting of both bump-and pit-type defects on the LTEM mask substrate has been successfully fabricated. It is seen that pit-type defects are less printable because they are more smoothed out by the employed MLM deposition process. Specifically, all bump-type defects print even at the smallest height split of 1.7 nm whereas pit-type defects print only at the largest depth split of 5.7 nm. At this depth, the largest nonprintable 1D and 2D defect widths are about 23 nm and 64 nm, respectively.

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Native defects in mask blanks is one of the key issues in extreme ultraviolet lithography. If defect-free mask blanks is the only solution, the resulting cost will be very high due to the low yield of such blanks. In this paper, we present a method for fabricating defect-free-like EUV masks by implementing several novel techniques such as global pattern shift, fine metrology-orientation and precise e-beam second-alignment from blank preparation to e-beam exposure. The mitigation success rate versus mask pattern density is simulated and verified by lithographic results using mitigated masks.Our methodology provides a way to achieve defect-free-like EUV mask blanks.